The invention concerns a sealing assembly for use in forming a fluid-tight chamber against a moving belt, such as a dual belt press.
There are numerous processing installation, in which conveyor belts, in particular steel belts, are used to carry goods wherein the goods are exposed to the effects of a gas or wherein the ooods release toxic gases that must be exhausted, without affecting the environment. Thus, for example, in a cooling belt installation for the solidification of liquid tar, a layer of tar flows over a weir and is deposited at a temperature of approximately 300.degree. C. in a relatively low viscosity state, onto a traveling belt. The tar is cooled on the belt by spraying the underside of the steel belt with water or the like, until the tar solidifies. The tar solidified in this manner may be processed into granules.
The hot tar emits vapors harmful to the environment, so the vapors are exhausted by means of exhaust hoods above the cooling belt and purified in an air cleaning installation. In known installations of this type it is a disadvantage that the exhaust hoods covering the belt are insufficiently sealed relative to the belt, so that in addition to the exhaust gases, surrounding air is also sucked in. This occurrence does not adversely affect the suctioning step itself, but it adversely increases the expense of the subsequent purification process due to the increased volume of gas to be cleaned. Thus, the inflow of uncontaminated air leads to an undesirable complication of the purification of exhaust gases.
If products are to be cooled or heated on a moving belt under the effect of a certain gas, such as an inert gas (e.g., in order to prevent the occurrence of certain chemical processes during the cooling or heating), the sealing problem becomes even more important, as the escape of the treating gas from the treatment chamber must be prevented.
Known arrangements exhibit only inadequate sealing means or none at all. This is mainly due to the fact that the materials usually employed for sealing, such as rubber or the like, cannot withstand the aforementioned high temperatures, e.g., approximately 300.degree. C. in some cases without being damaged. For this reason, sealing has been effected only by metal strips or the like, which however, cannot attain an optimum sealing action, as the moving surface of the belt is not straight. It has been discovered that steel belts deform under the effect of the high temperatures prevailing, for example, during the deposition of liquid tar, and in particular become wavy at the edges not covered by the tar, so that it is not possible in these locations to use stiff sealing strips.
In known dual belt presses, involving the creation of pressure chambers adjacent to the steel belts, similar problems arise. The membrane seals proposed for such installations (e.g., see German DE No. 33 10 700 Al) cannot provide a solution of the problem, as the sealing profiles are seated in stationary guide ledges.
It is an object of the invention to provide a sealing layout of the above-mentioned type so that even at very high temperatures the sealing of wavy or deformed belts becomes possible.